1.新增notifyIcon控制元件，並新增Icon，否則托盤沒有圖示（托盤右鍵選單也可直接在屬性裡新增）；

2.響應Form的Resize或SizeChanged訊息：

        // Hide to system tray
        private void Form1_Resize(object sender, EventArgs e)
        {
            if (this.WindowState == FormWindowState.Minimized)
            {
                this.Hide();
                this.ShowInTaskbar = false;
                this.notifyIcon.Visible = true;
            }
        }
 

3.雙擊托盤圖示恢復需要響應notifyIcon的DoubleClick訊息：

        // Show from system tray
        private void notifyIcon_DoubleClick(object sender, EventArgs e)
        {
            if (this.WindowState == FormWindowState.Minimized)
            {
                this.Show();
                this.WindowState = FormWindowState.Normal;
                notifyIcon.Visible = false;
                this.ShowInTaskbar = true;
            }
        }